Motorcycles, for example, are equipped with sealed meters or display devices such as tachometers, speedometers, odometers and trip odometers. These meters are sealed by a transparent member such as transparent glass or resin serving to keep water and dirt from getting inside the unit. FIG. 7 shows a seal configuration of this type of display window. Transparent member 103 is set via sealant material 104 into the lip 102 which is formed in the display window unit 101 of the case 100.
In the above-described unit, the transparent member 103 is tightly sealed in the display window 101 around the lip 102 of the display window 101 by means of sealant 104. However, because the assembly of these units requires that the edge of the transparent member 103 be positioned on the top surface of the lip 102 and that it be coated with sealant, it is impossible to use a sufficiently thick layer of sealant 104 and at the same time accurately position the transparent member 103 with respect to the lip.
Accordingly, when the sealed display device is exposed to heat, the differences in the thermal expansion coefficients between the case 100 and the transparent member 103 can cause the seal of the sealant 104 to be broken between the upper surface of the lip 102 and the transparent member 103.
It would be possible to resolve this problem of seal breakage by increasing the thickness of the sealant, but since this would involve broadening the gap between the transparent member and the lip, this would make positioning during assembly all the more difficult and detract from assembly productivity.
There is thus need for a means for covering the opening of an instrument such as a speedometer, tachometer and the like with a transparent member so that the transparent member is sealed to the housing of the instrument with a sufficiently thick layer of sealant to maintain a seal over a prolonged period of time, and which also facilitates production of the sealed unit.